(1) Field of the Invention
The present invention relates to a method and compositions for the treatment of fireblight in plants which is caused by Erwinia amylovora. In particular the present invention relates to the use of mixtures of a phage for the Erwinia amylovora and an enzyme produced by a phage for the Erwinia amylovora in the treatment of this plant disease.
(2) Prior Art
Fireblight disease in plants is caused by an extracellular polysaccharide produced by Erwinia amylovora. It is a large molecular weight polymeric anion which interferes with the transport of nutrients in the infected plant. The result is that the plant leaves and buds die from lack of nutrients.
Various methods have been suggested by the prior art for the treatment of fireblight. Included is the use of various antibiotics which kill the Erwinia amylovora. The problem with this method is that mutant strains are produced over time which are resistant to the antibiotic. Other methods suggested include applying other strains or species of bacteria usually of the genus Erwinia to the plant in order to displace the Erwinia amylovora by population dominance. The problem with this method is that it involves the release of large numbers of bacteria into the environment and it is not particularly successful.
Polysaccharide depolymerases have been described for bacteriophage infected bacteria, particularly Erwinia amylovora by Hartung, J.S. et al in Phytopathology 72 945(1982). Phage infection results in the induction of enzymes that degrade the capsular polysaccharide of the host. No use was described for the depolymerase enzyme which was in impure form.